Taking down the mast, I forgotto remove the pin at the base. Consequently, I had to shimmy the mast around at the base to get it off the ball. A small part of the mast base chipped off. Will this be a problem when I raise the mast next spring and start sailing?

Not typically a problem. The ball fits well into the casting. The pin is only used to secure the ball into the base for stepping and prevents you from pulling back and away from the ball. As long as you push forward while stepping the mast... it will stay in there.

I know for the Wave that it's supposed to stay in .... there's a thread on the Wave forum. I'd assume the directions are the same for the Getaway. When I 70-degree turtled in a Wave 10 days ago, I'd hate to think what would have happened if the mast and sail hadn't been held attached to the ball (by the pin)while upside down and planted in mud.

They also keep the base on the ball if the rig gets loose and you capsize. With a tight rig, not an issue really. Some take them out to avoid the type of damage you incurred if a shroud or forestay fails. I prefer to leave them in...